Thanks for posting pics. I like the out of tank and gravity flow design. I think that the area for algae growing can be improved.
What is the screen for at the top of the box? It might be reducing the light into the chamber IMO.
You could move the light source closer to the "box".
You could remove the yellow partial box lid and open it up for more area for algae growth. I would set a grid along the "floor" and place smaller grids along the four "walls".

Thanks for posting pics. I like the out of tank and gravity flow design. I think that the area for algae growing can be improved.
What is the screen for at the top of the box? It might be reducing the light into the chamber IMO.
You could move the light source closer to the "box".
You could remove the yellow partial box lid and open it up for more area for algae growth. I would set a grid along the "floor" and place smaller grids along the four "walls".

Hi thanks for you input. The screen is mainly for a lid purpose so it isnt exposed to daily living element. I.e dust.
I think i will add more grid to the walls and floor but i dont want to open the top too much coz i dont want to contaminate my aquarium. What if i cut out the same shape as the lamp on the mesh lid and lowered the lamp closer to it?

Understood (as I stare at the layer of dust on my shrimp tank lid...)
You could go with the cutout idea as long as the chance of splashing the light fixture is minimal.
You could try a sheet of acrylic instead for the top.
You could possibly experiment with other materials (such as the cloth mesh found on media bags) as an algae surface. Not sure if algae has an affinity for rougher, textured surfaces versus smooth surfaces.
I have seen some algae scrubber builds where the water twinkled down a fabric "curtain" right next to a light source. I'm certain evaporation was an issue with that design.

Understood (as I stare at the layer of dust on my shrimp tank lid...)
You could go with the cutout idea as long as the chance of splashing the light fixture is minimal.
You could try a sheet of acrylic instead for the top.
You could possibly experiment with other materials (such as the cloth mesh found on media bags) as an algae surface. Not sure if algae has an affinity for rougher, textured surfaces versus smooth surfaces.
I have seen some algae scrubber builds where the water twinkled down a fabric "curtain" right next to a light source. I'm certain evaporation was an issue with that design.

Ive done a slight change. Ive cut out a circle for the light. There is no way the water can splash because the hose is tight in the corner of my algae scrubber right close to the bottom, so no splash back.
Ive added a piece of roughened sewing mesh to the floor as suggested. Also the acrylic idea is a good one and i think i am going to purchase some on my next payday. Ive had to order more to do the sides so i have to wait. Heres some pics.